Being fit during the transition from the teenage years into adulthood may protect against heart disease decades later, a Swedish cohort study suggested.

Action Points

Being fit during the transition from the teenage years into adulthood may protect against heart disease decades later, a study found.

Note that obese men with a high aerobic fitness had a higher risk of MI than lean men with a low aerobic fitness.

Being fit during the transition from the teenage years into adulthood may protect against heart disease decades later, a Swedish cohort study suggested.

Men who had lower aerobic fitness levels when they were examined before entering mandatory military service at age 18 were more likely to have a myocardial infarction (MI) during a median follow-up of 34 years (P<0.001 for trend), according to Peter Nordstrom, MD, PhD, of Umea University in Sweden, and colleagues.

The relationship was consistent across categories of body mass index (BMI), but obese men continued to have higher rates of MI compared with their leaner counterparts regardless of fitness level, the researchers reported online in the European Heart Journal.

"Overall these findings suggest that high aerobic fitness in late adolescence may reduce the risk of MI later in life, although high cardiovascular fitness appears not to fully compensate for overweight or obesity with respect to this risk," they wrote.

The study comprised 743,498 Swedish men who were examined during conscription at an average age of 18.5. The evaluation included an assessment of aerobic fitness on a cycle test and various measures of muscle strength.

National registries were used to track the occurrence of MIs during follow-up.

After adjustment for age, BMI, comorbidities, education, blood pressure, and socioeconomic factors, an increase of one standard deviation -- or 15% -- in the level of aerobic fitness at age 18 was associated with an 18% lower risk of MI during follow-up (HR 0.82, 95% CI 0.80-0.85).

Men in the lowest fifth of aerobic fitness had about double the risk of MI seen in men in the highest fifth (HR 2.1, 95% CI 2.0-2.3).

The associations between various measures of greater muscle strength and reduced MI risk were weaker, but still statistically significant.

"Given the pronounced effects found, the low cost and easy accessibility of cardiovascular training, and the role of cardiovascular disease as a major cause of mortality and morbidity worldwide, these results are of interest with respect to public health," the authors wrote.

"However, it should be noted that the relationship between aerobic fitness and myocardial infarction is complex, and probably influenced by confounders not investigated in the present study," they added. "This could include a genetic predisposition to both a high physical fitness and a low risk of cardiovascular disease."

The researchers also examined whether a higher level of fitness could overcome the detrimental effects of obesity, and found that obese men who had the highest fitness level still had an elevated risk of MI compared with the leanest men (BMI under 18.5 kg/m2) who had the lowest level of fitness (HR 1.7, 95% CI 1.2-2.6).

"Our results do not support studies in middle-aged and elderly individuals suggesting that obese subjects with high physical fitness may have similar or even lower risk of cardiovascular disease, or death from cardiovascular disease, as normal-weight unfit subjects," the authors wrote.

They acknowledged that their study was limited by the inclusion of younger men only, the inability to establish cause-and-effect relationships, the lack of some covariate information (cholesterol, for example), and the inability to account for changes in fitness, blood pressure, and BMI during follow-up.

MedPageToday is a trusted and reliable source for clinical and policy coverage that directly affects the lives and practices of health care professionals.

Physicians and other healthcare professionals may also receive Continuing Medical Education (CME) and Continuing Education (CE) credits at no cost for participating in MedPage Today-hosted educational activities.